"MABEL!"
Stan's scream rips Dipper from the haze of his mind, the ache of his body hitting the floor. His head snaps up, eyes watering in the bright light flaring off the portal, to a silhouette caught in the center of it. Immediately, Dipper's heart stops. Mabel is caught in the pull of the portal, rapidly disappearing into the bright swirl of light.
Dipper can't tell if he's screaming her name, begging her to come back, over the roaring in his ears. Maybe it's the blood rushing through his body, maybe it's the whine of the portal; he can't tell. He's glad he's already on his knees or he'd be face down in the dirt from terror.
Then something collides with his shoulder, sending him sprawling sideways. It takes half a second to realize it was Grunkle Stan, hurling himself forwards to grab something. It takes the other half of that second to realize it's a piece of bright pink yarn, the same color as Mabel's sweater.
Dipper gets his feet under him and throws himself forward, the pull of the portal propelling him to Grunkle Stan's side in three steps. He curls the pink yarn around his hands as Grunkle Stan pulls it towards them.
"I'm sorry! I never meant for this to happen! I can't lose you, I can't lose either of you! No more secrets, no more, I promise! Just give her back!"
Grunkle Stan is crying, and Dipper isn't sure if he is too. Mabel's disappeared through the light, but the yarn is taunt in their hands; hope is on the other end. The light is beginning to flicker, and suddenly someone is stepping out.
But they're too big to be Mabel, so Dipper doesn't care. Grunkle Stan doesn't seem to care either as he keeps reeling in the yarn. Then, just as the portal begins to creak, as the light gets blinding, Grunkle Stan pulls hard on the yarn and Mabel appears.
Dipper thinks about Bill's nickname for her suddenly, as she's caught in the gravity flux caused by the portal; the light shines around her, burning brightly, just like a shooting star. Mabel comes hurtling towards them, and Grunkle Stan snatches her from the air, dragging Dipper into his arms as he turns his back on the portal as it gives way to darkness.
Mabel is sobbing into Grunkle Stan's shirt, her sweater more than half unraveled and tangled around them and between Dipper's fingers. Dipper presses his face right up against hers, and he's sobbing too, and she clings to both of them. Grunkle Stan is crying too, is face tucked into the spot where their head's meet, apologies falling into their hair.
Then suddenly Grunkle Stan is being pulled away from them, and Mabel's scream is something more horrible than even Grunkle Stan's. Before the man can get Grunkle Stan to his feet, Mabel leaps, and Dipper's right behind her. For as such as they are only twelve and still small, Dipper can be mean, and Mabel is worse. They hit the man at the same time, knocking him back and freeing Grunkle Stan from his hold.
Mabel does not stop there.
Her hands come up and slash at his face, catching under the mask he wears and knocking it askew. The man obviously isn't expecting her viciousness; he hesitates just long enough for Mabel to pull her arm back and punch him square in the face. He drops like a stone. Grunkle Stan drags her off him before Dipper can get near, tucking them both close to him as he drops to the ground.
Mabel folds herself around her twin as Grunkle Stan cradles them. Nothing can hurt them here. She's safe. She has Dipper and Grunkle Stan, and the portal is closed. Dipper finally voices the question she wanted to ask, but there is too much in her head.
"Who is that, Grunkle Stan?"
Soos, who had been ready to pull the man off Grunkle Stan if Mabel hadn't attacked him first, leans down and pulls the mask away, dropping it in shock.
"The Author of the Journals; my brother."